For cardiac arrest victims, resuscitation includes CPR chest compressions, rescue breathing, and defibrillation. Defibrillation is performed only when a reliable ECG can be obtained from the victim, and CPR chest compressions induce so much noise in the ECG signal that they must typically be halted for a quiet period of 12 to 15 seconds in order for an AED to obtain enough uncorrupted ECG data to make a reliable decision to shock a patient. During this quiet period, any blood flow induced by CPR compression ceases, and this is highly undesirable.
Also, as described in various references, including our prior patent, Sherman, et al. Chest Compression device with Electro-Stimulation, U.S. Pat. No. 6,213,960 (Apr. 10, 2001) it is beneficial to apply cardioverting shock from the defibrillator during specific periods in the CPR compression cycle, typically near the most compressed state of the chest, but best after the end of the compression or downstroke and as the chest is expanding in the upstroke. Though beneficial, synchronization of cardioverting shock with CPR chest compressions must be performed with two obstacles in mind. Firstly, it is best to avoid interruption of compressions, as is historically needed to obtain clean ECG data. Second, synchronized shock should not be performed if the CPR compression are provided manually by a CPR provider because it risks shocking the person (which can cause cardiac arrest in the CPR provider).
The first problem is solved by the motion artifact reduction techniques described in Halperin, C G Signal Processor and Method, U.S. Pat. No. 6,865,413 (Mar. 8, 2005). Halperin, and the See Thru CPR® technology embodied in various defibrillators, enable the analysis of the ECG signals while CPR chest compressions are ongoing. The second problem is addressed by providing CPR chest compressions with an automated chest compression device, such as ZOLL Circulations AutoPulse® chest compression device. ZOLL's automated external defibrillators (AED's) can be interconnected with the AutoPulse® device, and are programmed to apply defibrillating/cardioverting shock during a point in the compression cycle in which the heart is highly compressed and responsive to shock (this is provided in an operating mode that must be selected by the operator of the AED).
It would be beneficial to provide an AED which can analyze ECG data during CPR chest compressions without interconnection with a chest compression device, but is nonetheless operable to provide electrotherapy such as defibrillating and/or cardioverting shock while compressions are ongoing, and also provide electrotherapy synchronized to the compression cycle when CPR chest compressions are performed by an automated systems, but inoperable to provide synchronized defibrillating/cardioverting shock when CPR chest compressions are performed manually (by a person that may be in electrical communication with the CPR victim) while compressions are ongoing.